1. Field of the Invention
The present invention relates to an apparatus for covering a stack formed of articles supported on a support board with a stretch film and including at least four reef fingers movable in horizontal and vertical directions for picking up a film cover in four corners of the cover in a bellow-like manner, with each reefing finger having a somewhat L-shaped arch, and an adjustment drive unit associated with each reefing finger for folding, in the bellows-like manner, the film cover onto an associated reefing finger.
The present invention also relates to a method of covering a stack by using the above-described apparatus, with the method including moving the reefing fingers horizontally in four corner regions of the cover, so that the reefing fingers engage the cover in the four corner regions, placing the cover around the reefing fingers in a bellows-like manner, moving the reefing fingers away over a horizontal surface exceeding a horizontal dimension of the stack, and thereafter, pulling the cover over the stack, with the cover being initially supported on upper edges of the stack.
2. Description of the Prior Art
An apparatus and a method, which are described above, are disclosed, e.g., in German Patent No. 4,307,287. The method disclosed in the German patent has certain advantages over the previously known method and which consists in that for covering a stack having a variable cross-section along its height, the reefing fingers are displaced horizontally during their vertical movement, in order to accommodate the stack profile, in such a way that a stretched opening of the cover, which is formed by the reefing fingers, decreases or increases, with the reefing fingers being spaced from respective corner regions of the stack by the substantially the same distance. Thereby, it became possible, by controlling the horizontal movement of the reefing fingers, to adapt the position of the reefing fingers and, thus, the position of the film cover exactly to the profile of the stack during vertical displacement of the fingers and pulling of the cover over the stack. As a result, the released, by the reefing fingers, regions of the film cover are located at approximately the same distance from the stack circumference, whereby substantially uniform strips of the cover are released by reefing fingers. As a result of this, overstretching of film and damage of the cover, when a stack having a variable profile is covered, have been substantially reduced.
The method disclosed in German patent No. 4,307,287 insures a substantially good pulling of a horizontally stretched cover over the stack. However, under certain circumstances, an uncontrolled sliding of the cover from the fingers, in particular at the end of the pulling-over process, in the region of so-called bottom stretching, takes place. Therefore, measures need be undertaken to insure that the lower edge of the film cover lies beneath the pallet and does not ride up along the side walls of the stack.
German Publication DE 24 40 51 A1 discloses an apparatus for covering a stack of articles supported on a support board or pallet with a heat-shrinkable film and which includes finger-like elements for pulling a cover, which is formed of this film, over the stack. The finger-like elements are associated with spring-biased plate-shaped elements which should insure a uniform release of the reefed cover during its pulling. The disclosed apparatus does not provide for a controlled guiding of the corner regions of the cover.
Accordingly, an object of the present invention is to improve the sliding of reefed and horizontally stretched cover when the cover is pulled over the stack.